8-Cl-adenosine is an active metabolite of 8-Cl-cAMP responsible for its in vitro antiproliferative effects on CHO mutants hypersensitive to cytostatic drugs

• Published in: Cancer chemotherapy and pharmacology Vol. 48; no. 6; pp. 451 - 458
• Main Authors: ROBBINS, Susan K, HOULBROOK, Susan, PRIDDLE, John D, HARRIS, Adrian L
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01-12-2001
• Subjects: 2-Chloroadenosine - analogs & derivatives; 2-Chloroadenosine - analysis; 2-Chloroadenosine - metabolism; 2-Chloroadenosine - pharmacology; 8-Bromo Cyclic Adenosine Monophosphate - analogs & derivatives; 8-Bromo Cyclic Adenosine Monophosphate - analysis; 8-Bromo Cyclic Adenosine Monophosphate - metabolism; 8-Bromo Cyclic Adenosine Monophosphate - pharmacology; Adenosine - analysis; Adenosine - metabolism; Adenosine - pharmacology; Animals; Antineoplastic agents; Antineoplastic Agents - analysis; Antineoplastic Agents - metabolism; Antineoplastic Agents - pharmacology; Biological and medical sciences; Cell Division - drug effects; Chemotherapy; Chlorine Compounds - analysis; Chlorine Compounds - metabolism; Chlorine Compounds - pharmacology; CHO Cells; Chromatography, High Pressure Liquid; Cricetinae; Medical sciences; Pharmacology. Drug treatments; Temperature; Antineoplastic agent; Cell proliferation; Adenosine; Enzyme; Metabolite; Transferases; Rodentia; Cyclic AMP; Metabolism; In vitro; Biological activity; Vertebrata; Mammalia; Sensitivity resistance; Protein kinase; Analog; Animal; Established cell line; Metabolic activation; Tumor cell; Hamster; Cytostase
• ISSN: 0344-5704; 1432-0843
• DOI: 10.1007/s00280-001-0379-1

8-Cl-cAMP has been undergoing clinical trials as a potential chemotherapy agent, but there is much discussion in the literature as to whether the active agent is 8-Cl-cAMP itself, or its major metabolite, 8-Cl-adenosine. 8-Cl-cAMP is susceptible to the action of serum enzymes such as phosphodiesterases, and its metabolism when administered to cancer patients raises questions as to the mechanism of action of 8-Cl-cAMP. The stability of 8-Cl-cAMP when incubated with serum, and the effects of both 8-Cl-cAMP and 8-Cl-adenosine on the proliferation of variant lines of CHO cells hypersensitive to 8-Cl-cAMP were investigated. A solid-phase extraction (SPE) purification protocol and the HPLC method previously developed were used to determine 8-Cl-cAMP and 8-Cl-adenosine. Heat treatment of serum inactivated the enzymes in the culture medium responsible for activating 8-Cl-cAMP. Under these conditions 8-Cl-cAMP remained stable and there were no traces of its metabolite, 8-Cl-adenosine. Cell culture experiments showed that 8-Cl-cAMP only affected cell growth in medium that contained untreated serum. In contrast, 8-Cl-adenosine was shown to be growth inhibitory in medium containing either heat-treated or untreated serum. HPLC analysis of the culture medium from the cell culture experiments supported the hypothesis that 8-Cl-cAMP was only effective in inhibiting cell growth after metabolism to 8-Cl-adenosine. Thus further studies of this drug and its mechanism of action should focus on 8-Cl-adenosine.